A program of research on human adenoviruses is proposed which attempts an understanding of the genome of these oncogenic DNA viruses and how the genetic information is expressed and regulated in cells which produce virus upon infection or in cells which can undergo cell transformation. The problem is to be approached through isolation of messenger-RNA species for adenovirus proteins, with the ultimate aim of locating the information for these proteins on the viral DNA; through development of a system for obtaining, propagating and using a type of viral mutant, nonsense mutants, not now available for study; through induction and selection of temperature-sensitive mutants specifically blocked in viral regulatory functions; and through experiments designed to develop a system for the study of cytoplasmic-nuclear transport of proteins in virus-infected cells, in transformed cells, and in normal cells.